1. Technical Field
The invention relates to the field of magnetic sensors, and more particularly to a system and method for magnetic sensor transient interference avoidance and built in testing schemes.
2. Background Art
A magnetic activity sensor (such as a fluxgate) must be extremely sensitive to very low frequency magnetic fields in order to detect vehicles or armed personnel at appreciable distances. The circuitry associated with such sensors typically involves very high analog signal gains and very long time constants. This level of magnetic field is lower than is normally experienced near circuitry that includes supply current transients.
To simplify placement of a sensor, it is desirable to house it in the same enclosure with processing and communication circuitry, such as RF transmitters or serial interfaces. Unfortunately transients in such circuitry, when currents increase or decrease, can cause interference to the detectors and cause false alarms or degrade operation of background noise adaption algorithms. Long time constants (in the order of tens of seconds) which the circuit must incorporate can result in the sensor being unusable for appreciable times after such transients, limiting its usability.
Additionally, magnetic activity sensors, such as fluxgates and magneto-inductive devices are sensitive to small low-frequency magnetic fields. Testing of such devices requires generation of repeatable low-level fields relative to the position of the sensor.
One way to produce such a field is to use a pair of Helmholz coils to create a uniform field, in which the magnetic sensor device can be placed. Because the field is uniform, placement of the sensor within the coils is not critical, though orientation in the field must be controlled. Also, the coils must be large relative to the size of the device being measured and such testing requires the additional steps of placing the device in such a fixture to measure performance.
While the above cited references introduce and disclose a number of noteworthy advances and technological improvements within the art, none completely fulfills the specific objectives achieved by this invention.